Excretion is the removal of toxic materials and waste products of metabolism from the living organisms.
Excretion in plants
1. Respiration produces CO2 as a waste product.
2. Photosynthesis produces O2 as a by-product. Both gases are released through the stomata by diffusion.
3. Some deciduous plants excrete chemicals which may be left in the leaves in autumn. When the leaves fall, these substances are lost from the plants.
4. Water is produced during respiration and also removed during transpiration.